Computer and memory devices perform various functions including information processing and storage. Typically, in computer systems, the arithmetic, logic, and memory operations are performed by devices capable of reversibly switching between two states, often referred to as “0” and “1.” These switching devices are fabricated from semiconductor devices that perform these various functions and which are capable of switching between two states at a high speed.
For storage or processing of data, electronic addressing or logic devices may be made with inorganic solid state technology, and particularly crystalline silicon devices. The main device for performing these functions is the metal oxide semiconductor field effect transistor (MOSFET).
There is an increasing demand for making computers and memory devices faster, smaller and inexpensive. To meet these demands requires integration and fitting an ever increasing amount of transistors and other electronic structures onto pieces of silicon that are smaller than a postage stamp. This miniscule piece of silicon may contain tens of millions of transistors, were each transistor is as small as a few hundred nanometers. However, these silicon-based devices are fast approaching their fundamental physical size-limits.
Inorganic solid-state devices are generally encumbered with a complex architecture leading to high cost and a loss of data storage density. The circuitry of volatile semiconductor memories manufactured with inorganic semiconductor material must be constantly supplied with electric current, resulting in heating and high electric power consumption to maintain the stored information. Non-volatile semiconductor devices have a reduced data rate and relatively high power consumption as well as a high degree of complexity.
In addition, as the size of inorganic solid-state devices decreases and integration increases, the fabrication process is rendered more difficult because of the increase in the sensitivity to alignment tolerances of the device. Formation of features at small minimum sizes does not imply that the minimum size can be used for fabrication of working circuits. It is necessary to have alignment tolerances which are much smaller than the small minimum size, for example, one quarter the minimum size.
Generally, the control of a semiconductor device is accomplished through the utilization of electricity. A voltage is placed across the device to put it in a predetermined state, thus “controlling” it. Depending on the device being subjected to the voltage, it may store a value represented by the state or it may turn the device ON or OFF. If the device is a memory cell, it may be programmed to read, write or erase based on the voltage level and polarity. If the device is an LED, application of the voltage may turn the emitter ON or OFF, reduce its brightness or increase its brightness. Thus, it is imperative for proper operation of these types of devices that there is a means to control the application and level of the voltages across the devices. Current manufacturing techniques utilize additional external semiconductor devices for this purpose, such as transistors. These transistors are somewhat complex devices that require a multitude of fabrication steps to produce.